Fluorescent lamp type light-emitting diode (LED) lamps consume less power and longer lifespan, and thus are replacing widely used fluorescent lamps. The fluorescent lamp type LED lamps have the same external shape as the fluorescent lamps so as to be compatible with the fluorescent lamps.
However, when an LED lamp is repeatedly heated and cooled due to the heat generated from an LED, a body portion may be modified due to contraction and expansion, thereby creating a gap in a connecting portion between a cap and the body portion. In the long term, the gap may function as a path that allows external impurities to flow into the lamp, thereby causing malfunction or damages. Also, a dark space may be created due to inflow of impurities.